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  <div class="section" id="create-box-command">
<span id="index-0"></span><h1>create_box command<a class="headerlink" href="#create-box-command" title="Permalink to this headline">¶</a></h1>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>create_box N region-ID
</pre></div>
</div>
<ul class="simple">
<li>N = # of atom types to use in this simulation</li>
<li>region-ID = ID of region to use as simulation domain (optional)</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>create_box 2 mybox
create_box 1
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>This command creates a simulation box based on a specified region.
Either a <a class="reference internal" href="region.html"><em>region</em></a> command must first be used to define a
geometric domain and its <em>region-ID</em> must be specified as argument,
or a <code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code> command must be used
first. In the latter case the box defined by the
<code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code> is automatically used if
no <em>region-ID</em> is specified.</p>
<p>The argument N is the number of atom types that will be used in the
simulation.</p>
<p>If the region is not of style <em>prism</em>, then LIGGGHTS(R)-PUBLIC encloses the region
(block, sphere, etc) with an axis-aligned orthogonal bounding box
which becomes the simulation domain.</p>
<p>If the region is of style <em>prism</em>, LIGGGHTS(R)-PUBLIC creates a non-orthogonal
simulation domain shaped as a parallelepiped with triclinic symmetry.
As defined by the <a class="reference internal" href="region.html"><em>region prism</em></a> command, the
parallelepiped has its &#8220;origin&#8221; at (xlo,ylo,zlo) and is defined by 3
edge vectors starting from the origin given by A = (xhi-xlo,0,0); B =
(xy,yhi-ylo,0); C = (xz,yz,zhi-zlo).  <em>Xy,xz,yz</em> can be 0.0 or
positive or negative values and are called &#8220;tilt factors&#8221; because they
are the amount of displacement applied to faces of an originally
orthogonal box to transform it into the parallelipiped.</p>
<p>A <em>prism</em> region used with the create_box command must have tilt
factors (xy,xz,yz) that do not skew the box more than half the
distance of the parallel box length.  For example, if xlo = 2 and xhi
= 12, then the x box length is 10 and the xy tilt factor must be
between -5 and 5.  Similarly, both xz and yz must be between
-(xhi-xlo)/2 and +(yhi-ylo)/2.  Note that this is not a limitation,
since if the maximum tilt factor is 5 (as in this example), then
configurations with tilt = ..., -15, -5, 5, 15, 25, ... are all
geometrically equivalent.</p>
<p>See <a class="reference internal" href="Section_howto.html#howto-7"><span>Section_howto 12</span></a> of the doc pages
for a geometric description of triclinic boxes, as defined by LIGGGHTS(R)-PUBLIC,
and how to transform these parameters to and from other commonly used
triclinic representations.</p>
<p>When a prism region is used, the simulation domain must be periodic in
any dimensions with a non-zero tilt factor, as defined by the
<a class="reference internal" href="boundary.html"><em>boundary</em></a> command.  I.e. if the xy tilt factor is
non-zero, then both the x and y dimensions must be periodic.
Similarly, x and z must be periodic if xz is non-zero and y and z must
be periodic if yz is non-zero.  Also note that if your simulation will
tilt the box, e.g. via the <a class="reference internal" href="fix_deform.html"><em>fix deform</em></a> command, the
simulation box must be defined as triclinic, even if the tilt factors
are initially 0.0.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">If the system is non-periodic (in a dimension), then
you should not make the lo/hi box dimensions (as defined in your
<a class="reference internal" href="region.html"><em>region</em></a> command) radically smaller/larger than the extent
of the atoms you eventually plan to create, e.g. via the
<a class="reference internal" href="create_atoms.html"><em>create_atoms</em></a> command.  For example, if your atoms
extend from 0 to 50, you should not specify the box bounds as -10000
and 10000. This is because LIGGGHTS(R)-PUBLIC uses the specified box size to
layout the 3d grid of processors.  A huge (mostly empty) box will be
sub-optimal for performance when using &#8220;fixed&#8221; boundary conditions
(see the <a class="reference internal" href="boundary.html"><em>boundary</em></a> command).  When using &#8220;shrink-wrap&#8221;
boundary conditions (see the <a class="reference internal" href="boundary.html"><em>boundary</em></a> command), a huge
(mostly empty) box may cause a parallel simulation to lose atoms the
first time that LIGGGHTS(R)-PUBLIC shrink-wraps the box around the atoms.</p>
</div>
</div>
<div class="section" id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
<p>An <a class="reference internal" href="atom_style.html"><em>atom_style</em></a> and one of <a class="reference internal" href="region.html"><em>region</em></a> or
<code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code> must have been previously
defined to use this command.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="create_atoms.html"><em>create_atoms</em></a>, <a class="reference internal" href="region.html"><em>region</em></a>, <code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code></p>
<p><strong>Default:</strong> none</p>
</div>
</div>


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